It is proposed to develop a method for the analysis of lipofuscin substances in animal tissue via high performance liquid chromatography by use of a combination of fluorescence and flame ionization detectors. A profile of the lipofuscin substances will be interfractionated among the lipid classes by the proposed technique. The method will be applied to rats ranging in age from approximately one month to one year of age. The rats will be fed diets containing fat supplements of different fatty acid compositions. It is also proposed to determine the influence of the level and composition of the fat supplements on the biosynthesis of arachidonic acid as a function of aging.